Employees have a new favorite perk, and it’s not free craft-brewed beer, student loan repayment benefits or eco-friendly roof gardens at the office. It’s much simpler: More time off.

In its 17th annual employee benefits trend survey released this week, MetLife found that more people are interested in having an unlimited vacation policy than any other “emerging” perk, such as onsite medical clinics, subsidized egg freezing benefits or even paid sabbaticals. The idea was more appealing to employees of every age group than any other new benefit (with the exception of a phased retirement program to Baby Boomer-aged workers).

Yet despite that popularity, many companies are hesitant, said Todd Katz, executive vice president of group benefits at MetLife. While 72 percent of the 2,675 full-time employees who responded to the survey said they’d like to have an unlimited vacation policy, “only about a third of employers are considering offering it.”

The reasons may be obvious: Employers could fear that workers will take advantage of the policy and lose control over employees’ schedules. Or, they could worry – quite validly – that the opposite will happen, and too little guidance on vacation time could deter face time-driven workers from stepping away.

But whether they actually offer an “unlimited” policy or provide other ways for giving workers more time off, experts on work-life policies and organizational behavior say today’s always-on work environment makes the benefit that much more important.

“I think the value of time away from work has increased exponentially for people because there is no boundary – or there’s very little boundary,” said Cali Williams Yost, founder of Flex Strategy Group, a workplace consultancy. “The promise of a chunk of time where they can just forget about work is increasing at a rate that organizations are not leveraging.”

While employers have been adding family leave or responding to new state requirements for paid sick time, that’s different than making sure people feel that their vacation is protected or that an always-on, all-in approach to work is the only way to get ahead. More and more, people are rebelling against a “hustle culture” world, hoping to unplug in digital detoxes or turn their weekends into vacation since actual vacation time remains tethered to email.

“They want a break and they want it to be that they are off the clock,” said Yost.

Yet the challenge for employers in choosing what benefits to offer is that while workers may say they want more time off, they don’t always choose it when faced with a decision.

Harvard Business School assistant professor Ashley Whillans analyzed more than 42,000 employee responses in a Glassdoor survey, and found that benefits like parental leaves and flex time had more of an effect on job satisfaction than even tens of thousands of dollars in additional salary.

“Time is one of our most valuable resources that we often squander – we often don’t think it’s as important as it is,” Whillans said. “By focusing on non-time benefits, (employers) may be doing employees a disservice,” trying to cater to the benefits they think will make people happier, but don’t necessarily lead to better job satisfaction.

Yet employees also tend to choose money over time, consistently choosing a higher salary over more time off when presented with a choice, Whillans said. She studied employee rewards programs where workers got to spend “points” on items ranging from cash bonuses, movies passes or a watch to time-saving rewards like a housekeeping service, Task Rabbit gift card or even the ability to leave early from work for a period of time. They only chose rewards that gave them more time in 6 percent of cases.

“It’s one thing for companies to offer these kinds of fun or time-saving rewards but it’s another thing to get people to take them,” she said. Referring to surveys like the one from MetLife, she said “so many employers rely on these surveys to know what employees want, but they’ll say one and choose another.”